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https://github.com/jart/cosmopolitan.git
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155b378a39
The organization of the source files is now much more rational. Old experiments that didn't work out are now deleted. Naming of things like files is now more intuitive.
54 lines
3.2 KiB
C
54 lines
3.2 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/intrin/atomic.h"
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#include "libc/intrin/futex.internal.h"
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#include "libc/thread/thread.h"
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#include "libc/limits.h"
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/**
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* Waits for all threads to arrive at barrier.
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*
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* When the barrier is broken, the state becomes reset to what it was
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* when pthread_barrier_init() was called, so that the barrior may be
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* used again in the same way. The last thread to arrive shall be the
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* last to leave and it returns a magic value.
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*
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* @return 0 on success, `PTHREAD_BARRIER_SERIAL_THREAD` to one lucky
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* thread which was the last arrival, or an errno on error
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*/
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int pthread_barrier_wait(pthread_barrier_t *barrier) {
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if (atomic_fetch_add(&barrier->waits, 1) + 1 == barrier->count) {
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if (atomic_fetch_add(&barrier->waits, 1) + 1 < barrier->count * 2) {
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atomic_store_explicit(&barrier->popped, 1, memory_order_relaxed);
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do {
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_futex_wake(&barrier->popped, INT_MAX, barrier->pshared);
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} while (atomic_load_explicit(&barrier->waits, memory_order_relaxed) <
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barrier->count * 2);
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atomic_store_explicit(&barrier->popped, 0, memory_order_relaxed);
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}
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atomic_store_explicit(&barrier->waits, 0, memory_order_relaxed);
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return PTHREAD_BARRIER_SERIAL_THREAD;
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}
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do {
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_futex_wait(&barrier->popped, 0, barrier->pshared, 0);
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} while (atomic_load_explicit(&barrier->waits, memory_order_relaxed) <
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barrier->count);
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atomic_fetch_add(&barrier->waits, 1);
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return 0;
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}
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